Process for mixing gases, liquids or finely grained solids with a carrier gas and for the manufacture of reaction products

ABSTRACT

A process for the thermic treatment of a substance with a carrier gas comprising steps of: introducing the carrier gas from the bottom of a chamber while imparting a twist to the gas under high-kinetic energy; the chamber being axially symmetrical and having an upwardly tapering wall and a straight-walled portion at the top of the conical chamber; radially expanding the carrier gas to cause an upward flow thereof under the influence of centrifugal force, thereby creating an area of reduced pressure at the center of the chamber; diverting the upward flow to form a spiral; redirecting a portion of the gas to flow back through the area of reduced pressure and to mix with newly entered gas, thus creating an area of high turbulence; introducing the substance to be treated into the area of high turbulence and contacting it with the carrier gas; and removing the treated substance together with a portion of the carrier gas near the top of the chamber.

Niedner et al.

[ Mar. 7, 1972 PROCESS FOR MIXING GASES, LIQUIDS OR FINELY GRAINEDSOLIDS WITH A CARRIER GAS AND FOR THE MANUFACTURE OF REACTION PRODUCTSInventors: Peter Niedner, Muhlerstr. 104, Bendorf; Gerhard Diez,Koblenz-Olperstr. 21,

Bendorf-Sayn; Heinz Thubeauville, Roomarsheide 104, Bochum, all ofGermany Filed: Jan. 5, 1970 Appl. No.: 5,409 I Related US. ApplicationData Division of Ser. No. 576,507, Aug. 29, 1966, Pat. No. 3,459,949.

Foreign Application Priority Data Aug. 28, 1965 Germany ..O 11 087 0.8.CI. ..23/1 R, 23/87 R, 23/126,

23/139, 23/154, 23/166, 23/167, 23/200 Int. Cl. ..C0lq 1/00 FieldofSearch ..23/1,152,1B,126,l54,139, 231/87 R, 166, 167, 200

[56] References Cited UNITED STATES PATENTS 2,935,840 5/1960 Schoppe..23/1 R UX 3,098,704 7/1963 Schoppe ..23/1 R 3,495,949 2/ 1970 Neidneret al ..23/1 R X Primary Examiner-Edward Stern Attorney-Marmorek andBierman [5 7] ABSTRACT A process for the thermic treatment of asubstance with a carrier gas comprising steps of: introducing thecarrier gas from the bottom of a chamber while imparting a twist to thegas under high kinetic energy; the chamber being axially symmetrical andhaving an upwardly tapering wall and a straightwalled portion at the topof the conical chamber; radially expanding the carrier gas to cause anupward flow thereof under the influence of centrifugal force, therebycreating an area of reduced pressure at the center of the chamber;diverting the upward flow to form a spiral; redirecting a portion of thegas to flow back through the area of reduced pressure and to mix withnewly entered gas, thus creating an area of high turbulence; introducingthe substance to be treated into the area of high turbulence andcontacting it with the carrier gas; and removing the treated substancetogether with a portion of the carrier gas near the top of the chamber.

6 Claims, 7 Drawing Figures PATENTEDMAR 7 I972 SHEET 1 [IF 2 PATENTEDMAR7 I972 SHEET 2 BF 2 FIG.4A

PROCESS FOR MIXING GASES, LIQUIDS OR FINELY GRAINED SOLIDS WITH ACARRIER GAS AND FOR THE MANUFACTURE OF REACTION PRODUCTS This is adivision of applicants parent application Ser. No. 576,507, filed Aug.29, 1966, now US. Pat. No. 3,495,949, issued on Feb. 17, 1970 andentitled Device for Mixing Gases, Liquids or Finely Grained Solids Witha Carrier Gas and for the Manufacture of Reaction Products.

The invention relates to a process and a device for mixing of gaseous,liquid or finely grained solid substances with a carrier gas and for themanufacture of reaction products of one or more of such substances; alsofor the change of the physical state of one or more substances in whichthe carrier gas participates. The carrier gas thereby is introduced intoan axially symmetrical mixing or reaction chamber, respectively, whilegiven a twist or spin, and the substances are introduced simultaneouslyand are mixed or reacted in a zone of high turbulence. The latter isattained by suitably conducting the gas. The gases and substances leavethe chamber at the opposite end from the gas entrance in axial ortangential flow.

Reactors for carrying out processes requiring intimate mixing of thereactants are known. A carrier gas frequently is employed which, e.g.,in thermic processes, facilitates supply or removal of energy or whichpartly or entirely acts as reactant. Examples for reactions of thelatter type are combustions.

Examples of reactors wherein the carrier gas acts as transport mediumfor the energy are fluid bed reactors or spray driers. Therein thecarrier gas also removes moisture obtained from the substances.

However, reactors of this kind have drawbacks which severely limit theirapplicability. For instance, a heat treatment of finely grained solidsis not feasible in fluid bed reactors when these solids pass through amelting zone. Lump formation is likely to occur thereby, as is the case,e.g., in the refining of iron sulfate-heptahydrate. Spray driers usedfor the separation of substances such as wash powders (soap or detergentpowders) or of dried milk which has been dissolved or emulsified inliquids require long dwelling times in the drier and therefore largevolumes for complete treatment. Long dwelling times ensue from therelatively slight turbulence between heat carrier and the substances tobe treated. The danger that partially treated particles reach the drierwalls and cake on these walls necessitates a much larger volume of thedrier than theoretically corresponds to the dwelling time. Moreover,this large volume inhibits the application of high temperatures whichaccelerate reactions.

It is one object of the invention to intensify the mixing operation andthereby to accelerate the exchange of substances or the heat exchange,respectively, when a gas is the energy carrier. The salient feature isthe creation of high turbulence in a mixing chamber.

Experiments have shown that a particularly intensive turbulence zone canbe created by conducting two parallel gas streams in such a manner thatthey pass each other at substantially equal speed but in oppositedirection. This had previously been utilized in a mixing chamberwherein, e.g., a gas stream is carried with a twist into a chamber whichenlarges in the direction of the principal stream in such a manner thatthis gas stream follows the wall, reverses near the outlet and flowsback in the area of the axis of the chamber. A zone of high turbulenceis to form between the principal and the return flow wherein thesubstances are to be mixed. Such a turbulence zone actually can beattained. However, it has been found that this zone is very narrow, andit has further been established that some of the particles, introducedaxially into the chamber, penetrate this turbulence zone, impinge on thewalls prior to completion of the reaction and adhere thereto. In thecourse of the reaction, the steady supply of the substances leads toincreasing incrustation, so that the operation must be interrupted andthe chamber cleaned. Examples for 'this phenomenon are found upondrying, with splitting offof water of crystallization, of iron sulfateor iron chlorides. Similarly unsatisfactory results are obtained withexperiments in which a salt solution is sprayed into the chamber for thepurpose of separating solids by evaporation of the liquid component.

It is another object of the invention to eliminate these disadvantagessince it surprisingly has been found that this can be effected withmixing chambers equipped and operated in such a manner that the carriergas is introduced into one end of the chamber within the area of therotational axis with high kinetic energy, radially expanded along thewall under the influence of centrifugal force, diverted in the form ofan opening spiral, then redirected in the direction of the chamberoutlet and conducted to the outlet in spirally coaxial movement alongthe wall of the chamber which conically tapers. The substances to betreated are fed into the chamber within the rotational axis of themixing chamber either in the direction of the principal stream or inopposition thereto.

The invention now will to further explained with reference to theaccompanying drawings. However, it should be understood that these aregiven merely by way of illustration, and not of limitation, and thatnumerous changes may be made in the details without departing from thespirit and the scope of the invention as hereinafter claimed.

In the drawings, all of which are schematics,

FIG. 1 is an elevational view of the device according to.the invention;

FIG. 2 is a similar view as shown in FIG. 1 showing a diverted spiralgas flow therein;

FIG. 3 is a sectional view of an embodiment with built-in gas producer;

FIG. 3(A) is a view taken along lines A-A of FIG. 3;

FIG. 4 is a sectional view of another embodiment showing a concentricalring burner; and

FIG. 4(A) is a view of FIG. 4 taken along lines A-A thereof.

Referring now to these drawings, the carrier gas in introduced into theaxially symmetrical chamber shown in FIG. I rotating with high-kineticenergy within the area of the rotational axis of the chamber. The inletfor the carrier gas is located at 12 and the provisions for creating thetwist or spin of the gas are disposed at ll. These provisions are of theconventional kind and are not shown per se in the drawings. They mightconsist of guide vanes, an entrance spiral, or the like. After the gashas passed the inlet 12 it suddenly is expanded under the influence ofthe centrifugal force and flows radially into the area 13 in the form ofan opening spiral. The gas is deflected, after passing a given pathlength, in the direction of the rotational axis and flows spirally andcoaxially to the axis of the chamber in the direction of the chamberoutlet 17 through a conically tapering area of the chamber.

The ensuing spiral flow of the gas is illustrated in FIG. 2.

The radial expansion of the carrier gas under the influence of thecentrifugal force, as mentioned, creates, within the area of therotational axis 14, a zone of diminished pressure, the same as resultsin the stream about a radial compressor or a centrifugal pump. This zoneof reduced pressure effects a partial reversal of the gas stream beforeit leaves the chamber and a backflow against the principal flow withinthe area of the rotational axis 14. Between the principal stream nearthe wall and the backflow, an extensive zone 15 forms which exhibitsintensive turbulence wherein very intimate mixing of carrier gas and thesubstances to be treated or the intended reaction, respectively, occurs.The substance to be treated enters the chamber through conduit 16 which,in the case of the introduction of a liquid, may be provided with anozzle 18. The high turbulence of the carrier gas precludes contact ofthe substances with the chamber wall at any time.

FIGS. 3 and 3(A) show an arrangement for simultaneous production of thegas which is to serve as carrier from liquid or gaseous fuels. A ringchamber is provided below the reactor for the combustion which is firedtangentially in such a manner that the hot gas stream, prior to itsentry into the devices providing rotation, obtains a twist or spin inthe same direction. By suitable shaping of the ring chamber andsynchronization with the cross section of the reactor inlet, the

special twisting devices, such as guide vanes, spirals, bends, or thelike, can be dispensed with entirely.

The arrangement in accordance with FIGS. 4 and 4(A) show a combustionchamber which is disposed concentrically with the reactor in the form ofa ring chamber. Aside from the advantages described in connection withFIGS. 3 and 3(A), this disposition of reactor and combustion chamberfacilitates not only lower height of the entire unit but also thecombination of a common wall between combustion chamber and reactionspace. For reactions which can be carried out at temperatures abovel,000 C., this embodiment is useful from a heat-economical point ofview. However, the particular advantage of this embodiment is to befound in the feature whereby the heat flow proceeds from the combustionchamber through the common wall with the reactor into the reactorsinterior whereby a certain amount of heat radiation from the reactorwall into the reactor space influences the course of the reaction in asurprisingly favorable manner.

For the measurement proportions of the mixing and reaction chamber,certain ranges have been established as particularly advantageous. Theseare shown in FIG. 5, as follows:

The largest cross section D opportunely is 1.4 to 3 times that of thesmallest cross section d. The smallest cross section d is to be in thearea of the chamber outlet. The effective height H of the chamber is tobe 1.5 to 3.2 times as large as the smallest cross section d. The inletcross section q preferably is 0.06 to 0.4 times the chamber crosssection; and the chamber wall surrounding the inlet cross section is toform an angle to with the rotational axis which is between 60 and 120.

The substance exchange or heat exchange values obtained by means of thehigh turbulences enable high performance at small dimensions of thedevice. The volume of the apparatus according to the invention can be aslittle as one one-hundredths of that of a conventional spray evaporator,for instance. Because the surfaces also are comparatively small, heatlosses are considerably lowered. Moreover, small dimensions saveconstruction costs and permit the use of materials which facilitatereactions at such temperatures which had not been feasible on aproduction scale with conventional equipment.

In the treatment of liquids which are introduced into the chamber by wayof a nozzle, as shown as 18 in FIG. 1, it has been found that the dropsare torn steadily diminishing into streaks or schlieren in the zone ofhigh turbulence so that they attain a drop size upon the start of theactual reaction which is much smaller than those attained withconventional nozzles. Consequently, very large surface per unit ofsubstance and, hence, an unexpectedly high reaction speed are obtained.Whereas in a conventional spray process the end product is a hollowsphere or of a half moon shape, the process in the chamber according tothe invention leads to finely linked, surface-active structures. Thisfacilitates in the ensuing separation of solids from the gasunexpectedly high-separation yields in conventional cyclones.

The field of application primarily is that of thermic processes.Experiments have shown that the temperature imparted to a particle ofthe substance largely corresponds to the exit temperature of the gasfrom the reactor. This enables adjustment and control of a givenreaction temperature with simple means. This is particularly significantfor the execution of reactions whose minimum and maximum temperaturesare within narrow limits. No local overheating has been observed, due tothe high turbulence.

Examples for thermic processes which can successfully be carried out inthe reactor according to the invention are, among others, l drying ofiron sulfate-hydrates with splitting off of water of crystallization,which is a process wherein the substance passes through a melting zone;(2) the evaporation of sulfuric acid solutions containing iron sulfatefor the purpose of separating dry iron sulfate, a process which requiresthe maintenance of minimum and maximum temperatures within a narrowrange; (3) the evaporation of metal chloridecontaining acid solutionswith simultaneous thermic reaction of the metal chlorides to metaloxides and HCl gas; and (4) the thermic decomposition of crystallineiron sulfate to iron oxides, sulfur oxides and steam.

However, these applications are merely examples, and other processes canreadily be carried out in the device according to the invention.

We claim as our invention:

1. A process for the thermic treatment of at least one substanceselected from the group consisting of gases, liquids and finely grainedsolids with a carrier gas which comprises introducing said carrier gasfrom substantially the bottom of a chamber while imparting a twist tosaid gas and under highkinetic energy; said chamber being axiallysymmetrical and having an upwardly tapering wall and a straight-walledtop portion of a cross section substantially the width of thesmallestpart of the cone; radially expanding the carrier' gas to causean upward flow along said conical wall under the influence ofcentrifugal force thereby creating an area of reduced pressure in thecenter portion of the chamber; diverting said upward flow to form anopening spiral; redirecting a portion of said gas to flow back throughsaid area of reduced pressure and to mix with newly entered gas thuscreating an area of high turbulence in said reactor; introducing thesubstance to be treated into said area of high turbulence and intimatelycontacting it with said carrier gas; said substance thus being precludedfrom contacting the chamber walls; and removing the substance thustreated, together with a portion of said carrier gas, from the chambernear the top thereof.

2. The process as defined in claim 1, wherein said substance is fed intosaid chamber from the top thereof.

3. The process as defined in claim 2, wherein said substance is fed intothe axial area of said chamber.

4. The process as defined in claim 1, wherein said thermic treatment isa process in which the physical state of the substance thus treated ischanged.

5. The process as defined in claim 1, wherein said thermic treatmentresults in a chemical reaction.

6. The process as defined in claim 5, wherein said carrier gasparticipates in said reaction.

2. The process as defined in claim 1, wherein said substance is fed intosaid chamber from the top thereof.
 3. The process as defined in claim 2,wherein said substance is fed into the axial area of said chamber. 4.The process as defined in claim 1, wherein said thermic treatment is aprocess in which the physical state of the substance thus treated ischanged.
 5. The process as defined in claim 1, wherein said thermictreatment results in a chemical reaction.
 6. The process as defined inclaim 5, wherein said carrier gas participates in said reaction.